The present invention relates to a test of a nonvolatile memory device and, more particularly, to a method of testing a nonvolatile memory device, in which after a program is performed on the entire pages, fail status bit information is output on a memory-block basis.
Flash memory, i.e., nonvolatile memory, is generally classified into NAND flash memory and NOR flash memory. NOR flash memory has a structure in which respective memory cells are connected to bit lines and word lines independently and therefore has an excellent random access time characteristic, whereas NAND flash memory has a structure in which a plurality of memory cells is connected in series and only one contact is required on a per cell-string basis and is therefore excellent in the degree of integration. Thus, the NAND structure is usually used in high-integrated flash memory.
A well-known NAND flash memory device includes a memory cell array, a row decoder, and a page buffer. The memory cell array is comprised of a plurality of word lines extending in rows, a plurality of bit lines extending in columns, and a plurality of cell strings, each corresponding to bit lines.
This nonvolatile memory device performs a test for determining whether an operation of a memory cell is normal in order to operate a chip normally. When a memory device operates, a normal (pass) status may result when reading data, but a fail status may result when the state of the data is checked. Accordingly, a repair operation is performed on a column having a faulty memory cell so that a memory device can operate normally.
In the case in which a normal pass status results at the time of data reading, but a fail status results at the time of state check, a repair operation has to be performed using a state bit screen operation.
FIG. 1 is an operation flowchart showing a general flash memory device.
Referring to FIG. 1, when an operation begins in test mode (S101), a program operation is performed on a page basis (S103). Program data is read into a page buffer and the data read into the page buffer is scanned (S105). Pass or fail status is determined according to the result of the page buffer scan (S107).
The program operation and the page buffer scan on a page basis are performed on the entire pages, respectively. If the program and scan operations are performed up to the last page (S109), the test is finished.
The state bit screen operation is used as a combination of an algorithm for an operation command and a test bit to be programmed into a page. The state bit screen operation wastes a lot of test time since, after data of a page buffer is output for every page, the output data has to be checked.